WEATHER

Cool weather has been the norm for the past 3 weeks. One 7-day period early in May accounted for 40% of the base 42 degree days and 53% of the base 50 accumulation for the month. Since 5/9 the highest daily maximum temperature recorded at the NWMHRS has only been 71º F. Evaporation for the past 7 day period has remained fairly low at approximately 1.1". 

GROWING DEGREE DAY ACCUMULATIONS as of May 30th at the NWMHRS

Year       2000      1999      1998      1997
GDD42    693        728         878        339
GDD50    328        372         490        121

GROWTH STAGES:
Apricot: Harcot -- 30 mm
Plum: Stanley -- 10 mm
Pear: Bartlett -- 13 mm
Apple: Red Delicious -- 9 mm
Sweet Cherry: Napoleon -- 13 mm
Tart Cherry: Montmorency -- 12 mm
Grapes: Chardonnay -- 4"-8" shoots

COMMODITY REPORTS

As reported last week, the tart cherry crop is much smaller than anticipated at the time of bloom. Many growers are estimating crops to be significantly smaller than in 1999.

Apples are currently at a critical time for thinning. Trying to find a spray window when the temperatures are greater than 70º F has been difficult. Growers should check closely to be sure that thinning is needed. Codling moth trap catches are up, but the adults are still slow to emerge due to the cool temperatures. A few high-pressure blocks, typically older standard blocks, have biofixed already. The first sprays should go on 250 DD base 50 after biofix. Spotted tentiform leafminer mines have not shown up yet. I suspect that both predation and the frosts have taken their toll on larvae, but nonetheless, mines should be showing up soon. Plum curculio will become active on apples later in the week, as the fruit sizes more. Apple scab has not shown up yet in abandoned apples. Currently we are at 1050 DD base 32 from green tip. All spores should be mature at this time, however at least one more good rain is needed before we can call an end to the primary scab season. Blossom blight symptoms from the May 7^th infection should be showing by the end of the week. Trauma blight symptoms (if they show) won't be showing up until early next week 
 

ProGibb sprays are starting to go on in the warmer areas of NW Michigan. Trunk sprays can be applied to control the borer complex. Lesser peach tree borer trap catch was up to 20 per trap at the NWMHRS. Plum curculio activity has been slow, due to the cool temperatures. With warm weather forecasted, activity should pick up. Sweet cherries, plums, peaches and high pressure blocks of tart cherries should all be protected at this time. With tart cherries we are currently at 152 DD base 50 after full bloom. Insurance sprays are needed to control plum curculio at the 375 DD mark (this model should only be used where plum curculio pressure is low). Cherry leaf spot is starting to show up in abandoned cherries. Growers should check their orchards closely for the presence of this disease and tighten up their spray program if needed.

Insect activity in wine grapes is still very light throughout the area. Grape berry moth trap catches at the NWMHRS averaged 3 per trap. A post bloom insecticide treatment should take care of this pest in vineyards with pressure. Grape leafhopper and potato leafhopper should be showing up soon. Scouts have reported that symptoms of powdery mildew and phomopsis are now appearing in many vineyards. Growers should get ready for pre-bloom powdery mildew controls. Frost injury to vines occurred at scattered sites. In some young vineyards which had tall cover crops remaining in the row middles, cold air apparently settled in the "valleys" between the cover crop bands and caused significant injury to young vines. Nearby vines of similar ages suffered far less injury where the cover crop had been mowed or tilled in. Tilled or bare ground (preferably moist) holds more heat than grass middles and releases that heat at night when frost protection is needed. 

MISCELLANEOUS
By Jim Nugent

Cool conditions have made it difficult to find the correct weather for applying GA on cherries and chemical thinners on apples. However, the timing for application is still good, but in much of NW Michigan it will need to be done soon. Expected warmer weather in the coming days should give better temperatures for application, but will also speed tree development. 

Spreading Limbs in First and Second Year Trees

The best time to spread newly growing shoots to cause wide crotch angles is when shoots are 3-5". Second leaf trees are currently at this stage, though newly planted trees may need to do a little more growing. At this stage, the limbs can easily be spread by pinning a clothespin onto the leader immediately above a potential small shoot. This can improve the selections available as scaffolds next spring. Regular clothespins usually work well, but some larger trees (particularly sweet cherries) really need a clothespin that opens extra wide. Extra large clothespins can sometimes be found at Meijers stores, but they can probably be purchased at a better price through LDK Sales, 1755 Woodmar Ct., Howell, MI 48843, tel. 517/540-0984. Toothpicks can also be used to spread small new shoots in apples, but don't use in any stone fruits.

Soil Moisture and Irrigation

Soil moisture should be adequate at this time, but with the leaf area expanding, ideally most trees would do best if rainfall equaled about 75% of evaporation. Apple trees on M9 size rootstocks probably should be irrigated to replace closer to 100% of evaporation, and Mark rootstock trees need even more water. So far in May evaporation has totaled 5.23", while precipitation at the NWMHRS has totaled 3.19". Consequently, rainfall is at 61% of evaporation. So, while soil moisture is not low at this time, it is time to get the irrigation systems operational for this season.
 
 

Please send any comments or suggestions regarding this site to: 
Bill Klein, kleinw@pilot.msu.edu

Last Revised:5-30-00